1. Technical Field
The invention relates to a method for determining points in space for guiding the movement of a robot arm, and, more particularly, for determining break points in successive linear motion sections which in total approximate an ideal robot arm motion trajectory.
2. Description of the Prior Art
For controlling the motion of robot arms, a desired ideal robot arm motion trajectory is resolved into a series of N short individual linear segments which approximate the trajectory. Each linear segment is determined by a beginning and an end point. A determination of break points, points at which the robot arm must physically change linear direction, should relate to a predetermined position tolerance of the particular robot arm, the position tolerance being defined as the minimum distance a given robot arm is capable of traveling without appreciable error. Such a system which considers the predetermined position tolerance of a particular robot arm is known. Due to the fact that only the robot arm motion break points need to be provided to a control system for the robot arm and movement between these break points is controlled by an interpolator, a fast and technically simple control of the robot arm motion trajectory is obtained.
A robot arm trajectory, however, need not comprise as many motion sections as linear segments Consequently, the problem with prior art robot arm control is that they do not tend to optimize the determination of break points for the robot arm motion sections. The determination of the break points, in prior art systems, is done individually by means of a manual-motion key at a robot arm control panel or through a particular calculation algorithm developed by a computer programmer. Thus, in the case of manually manipulating a robot arm through its path, the determination of the break points depends on the skill of the operator. In the case of a separate computer calculated determination, the skill of the programmer is critical. Both prior art methods lead to reproducible solutions only if the trajectory relates to clearly distinguishable geometric forms.
Prior systems of this nature are disclosed in French Pat. No. 1,557,915 and U.S. Pat. No. 4,263,538, the disclosure of which is hereby incorporated by reference.
Thus, there is a need in the art for an automatic method of determining break points which efficiently takes into consideration the position tolerance of the particular robot arms and, at the same time, limits the number of necessary break points to a number less than were involved in an initial resolution of the trajectory path.